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October 2, 2009

Basking Shark Washed Ashore in Sanderling, NC

Here are a few photos of a basking shark that washed up on shore near Duck, NC about two weeks ago. The shark was over 20' in length.

It's always a sad day when something like this happens but it is also an opportunity for onlookers to get an up close look at an elusive giant of the sea. And ultimately, these encounters help people think a bit more about marine conservation (no matter the circumstances). I was unable to find any information on the cause of death.

Since I wasn't very familiar with this species of shark, I figured others like me might find this interesting.

Photobucket

Photobucket Photos Courtesy of Carolyn J. Drost

**NOTE 12/18/2010: Ms. Drost's top photo has been used in a newly created urban legend. Read more here

Here's some select info on the basking shark from wikipedia:

The basking shark, Cetorhinus maximus, is the second largest living shark, after the whale shark. It is a cosmopolitan species — it is found in all the world's temperate oceans. It is a slow moving and generally harmless filter feeder. This shark is called the basking shark because it is most often observed when feeding at the surface and appears to be basking.

The basking shark is a coastal-pelagic shark found worldwide in boreal to warm-temperate waters around the continental shelves. It has traditionally been observed in waters between (46 and 57° F) but recently they have been confirmed to cross the equator. It is often seen close to land and will enter enclosed bays. The shark will follow concentrations of plankton in the water column and is therefore often visible on the surface. They are a highly migratory species leading to seasonal appearances in certain areas of the range. The basking shark is found from the surface down to at least 3,000 ft.

The basking shark is one of the largest known sharks, second only to the whale shark. The largest specimen accurately measured was trapped in a herring net in the Bay of Fundy, Canada in 1851. Its total length was 40.3 ft, and it weighed an estimated 19 tons. Normally the basking shark reaches a length of between 20 ft and a little over 26 ft. Some specimens surpass even 33 ft, but after years of hard fishing, specimens of this size have become exceedingly rare.

Basking sharks possess the typical lamniform body plan (distinguished by possessing two dorsal fins, an anal fin, five gill slits, eyes without nictitating membranes, and a mouth extending behind the eyes) and have been mistaken for great white sharks. The two species can be easily distinguished, however, by the basking shark's cavernous jaw (up to 3ft in width, held wide open while feeding), longer and more obvious gill slits (which nearly encircle the head and are accompanied by well-developed gill rakers), smaller eyes, and smaller average girth.

The basking shark is a passive filter feeder, filtering zooplankton, small fish and invertebrates from up to 2,000 tons of water per hour. Unlike the megamouth shark and whale shark, the basking shark does not appear to actively seek its quarry, but it does possess large olfactory bulbs that may guide it in the right direction. Unlike the other large filter feeders, it relies only on the water that is pushed through the gills by swimming; the megamouth shark and whale shark can suck or pump water through their gills.

Basking sharks are not considered dangerous to humans but contact with their skin should be avoided because the large dermal denticles have been known to inflict serious damage to divers and scientists. The giant sharks are generally considered tolerant of humans but have been known to attack boats after being harpooned.

Historically, the basking shark has been a staple of fisheries because of its slow swimming speed, unaggressive nature and previously abundant numbers. Commercially it was put to many uses: the flesh for food and fishmeal, the hide for leather, and its large liver (which has a high squalene content) for oil. It is currently fished mainly for its fins (for shark fin soup). Parts (such as cartilage) are also used in traditional Chinese medicine and as an aphrodisiac in Japan, further adding to demand.

As a result of rapidly declining numbers, the basking shark has been protected and trade in its products restricted in many countries. It is fully protected in the UK, Malta, Florida and US Gulf and Atlantic waters.


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